1. Field
The invention relates to wireless communications. More particularly, the invention relates to methods and apparatus for supporting multi-hop peer discovery in peer-to-peer wireless networks.
2. Background
Wireless communications continues to grow in demand and has become an integral part of both personal and business communications. Wireless communications allow users to transmit and receive data from most anywhere using wireless networks and wireless devices such as laptops, cellular devices, iPhones®, BlackBerrys®, etc.
Wireless fidelity (WiFi) describes the wireless networks that adhere to the specifications developed by the Institute of Electrical and Electronic Engineers (IEEE) for wireless local area networks (LAN). WiFi devices are certified to be interoperable with other certified WiFi devices using the 802.11 standard of the IEEE. These WiFi devices allow over-the-air interfaces in order to create a wireless network for facilitating data transfer.
Generally, wireless networks are established through mobile devices communicating with one or more base stations, access points or access routers. A base station is a radio receiver/transmitter that serves as a hub for wireless networks. A base station typically includes a low-power transmitter and a wireless router. An access router may be configured as an access point that covers a geographic range or cell and, as the mobile device is operated, it may move in and out of these geographic cells.
Some wireless networks can be constructed utilizing solely peer-to-peer communications without utilizing base stations, access points, or access routers. Such wireless networks are sometimes referred to as WiFi networks. Communications in such networks may, in some cases, be limited to exchanges between mobile devices that are within direct wireless transmission range of each other, while in other cases multi-hop forwarding between non-adjacent mobile devices may be supported. Various techniques may be used to maintain connectivity and/or forward information as the topology of the wireless network changes (e.g., as mobile devices join the network, leave the network, or move within the network). Some networks can also be constructed utilizing a combination of peer-to-peer communications as well as communications with base stations, access points, or access routers.
As mobile devices move in and out of wireless networks, the potential for higher layer communications with other mobile devices may be determined based on a process of peer discovery. To enable peer discovery, information associated with a mobile device (e.g., identifier, how to establish communications, and so forth) is advertised or announced (e.g., broadcast) to other mobile devices within a range. In a wireless network, peer nodes or devices discover each other by periodically transmitting and detecting peer discovery signals, which carry unique node identifiers (IDs).
The range of operation of peer discovery can be extended by increasing the transmission power of the node's peer discovery signals. Increasing the transmission power however, results in several drawbacks such as a reduced battery life, a decrease in the spatial reuse of resource units (time and frequency) utilized for transmission of peer discovery signals, and an increase in the de-sense probability. As one would expect, an increase in the transmission power of peer discovery signals results in a reduction of the battery life of the node (e.g., mobile device). An n-fold increase in the distance between nodes requires an n2-fold increase in the resource units. Also, an increase in the de-sense probability means that nodes wishing to discover far-away nodes get saturated by high-power peer discovery signals transmitted by near-by nodes.
Therefore, it has been recognized by those skilled in the art that a need exists for methods and apparatus for extending the range of operation of peer discovery without the aforementioned drawbacks.